The 3rd Generation Partnership Project (3GPP), acting as an important organization in mobile communication field, greatly pushes the standardization of Third Generation (3G) techniques and has proposed a series of standards including Wide Code Division Multiple Access (WCDMA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA) and so on.
Along with the development of communication techniques towards mobility and broadband, power saving problem of user equipment (UE) has attracted widespread attention. Many communication standard organizations have considered the power saving problem, when making relevant standards. In particular, access networks of future mobile communication systems will be based on Internet Protocol (IP) technique for data transmission. The burst of IP packets and the share of transmission channels among users make the data arrived at the UE in a discontinuous manner. Therefore, it becomes more important to save battery power of the UE.
In the mobile communication system, information exchange between the UE and an access network relies on power supply of both sides. The UE can be a cell phone, laptop and Personal Digital Assistant (PDA) which runs on battery power. Therefore, to lower power consumption and prolong standby and service time of the UE become a key problem for designing the mobile communication system. In order to lower the power consumption of the UE, Discontinuous Reception (DRX) mode is employed in 3GPP standard. In particular, in the DRX mode, the UE monitors a channel and receives downlink services in a pre-defined time interval negotiated with the access network, thereby reducing unnecessary time for monitoring the channel and reducing power consumption of the UE.
In operation, when the UE is connected to a network, the UE and the network negotiate the connection details. In some systems, the UE will enter a “sleep” state and wake periodically to “listen” for paging messages, or be in an active state when a paging message can be received. When sleep states are used, part of the negotiation of the UE with the network may be to determine and set a sleep period, or a period of inactivity. Thus, the network knows when the UE will be expecting paging signals, and can transmit paging signals during a period of time when the UE will be listening for such paging signals.